| Speeding up the transition to clean renewable energy is one of the best ways to curb the dangers of carbon pollution that cause the climate changes.Solar power is one of sustainable and clean energy sources.Abounding type of solar power is photovoltaic PV,so it needs to be integrated into the utility grid to reduce the amount of burning fossil fuel,which causes the pollution problem.Besides,different DC voltage levels,in the medium voltage bus(MVB),are needed to fulfil the customer expectation and to harvest the solar power into Future Renewable Electric Energy Delivery and Management(FREEDM)system.Therefore,this thesis discusses the integration of PV power with the main power grid via reciprocating bus based on power electronic transformer(PET).Different input and output connections are used according to the required current and voltage ratings of the FREEDM system.The possible configurations of connecting PETs are input parallel output series(IPOS),input series output parallel(ISOP),input series output series(ISOS)and input parallel output parallel(IPOP).Among these four configurations ISOP is used in several applications.The main advantage of using ISOP configuration is the connection between MVDC and low voltage DC(LVDC)with galvanic isolation.Reciprocating bus is created by changing the connection configuration of PETs in the secondary side from ISOP to ISOS for two lower PETs in the presented diagram to provide different voltage levels,which are 10KV and 20KV,in the MVB.While the other PET is configurated permanently with ISOP.10KV bus is the main bus to feed the load and 20KV bus is used to integrate the PV power into the FREEDM system;in fact,it can feed the load from the solar power or from the grid at the same time.Rewarding of using PET is controllable,efficient,and cheaper as compared with power transformer.The scope of this thesis is not limited to dc reciprocating bus only,the research has been done on PET application in FREEDM system.Simulation results validate the effectiveness and superiority of proposed diagrams in this thesis.They are verified by PSCAD/EMTDC software. |
